Noritz NR111-DV-NG Residential Tankless Water Heater can provide endless hot water for up to 4+ showers. With its Quick-Connect system, two identical heaters can be connected to meet the high demand of today's luxury homes. To accommodate the higher flow rate demand, these units have a dual flame burner, a redesigned heat exchanger and 25% thicker copper piping. No other tankless water heater in its class can beat its performance, dependability, and quality. Built-in features include safety lock-out, freeze protection, and high elevation adjustment. Available in Natural Gas models, the 0931 Series Water Heater is for indoor use with direct venting.